Strange Signal at Galactic Center–Is It Dark Matter?

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Artist's conception of the Milky Way surrounded by a dark matter halo. Image: ESO/L. Calçada

Are there dark doings near the center of the Milky Way? That may be so when it comes to the collision of dark matter particles. Although such particles are invisible, we could still theoretically see the mess they make when they collide. It’s this idea that leads physicists to scour the galaxy for some glimmer of dark matter collisions. Spot a line produced by a pair of gamma-rays emanating from just the right spot and you may have found coveted clues to the dark matter mystery.

Now a collaboration of scientists using the Fermi Gamma-Ray Spacecraft’s Large Area Telescope instrument (Fermi–LAT) has confirmed seeing an unusual gamma-ray line near the galactic center. If the finding stands up to further scrutiny, it’s possible this line comes from the annihilation of dark matter.

In April theoretical physicist Christoph Weniger, now at the GRAPPA Institute in Amsterdam, analyzed Fermi–LAT’s publicly available data and spotted a strange gamma-ray line near the galactic center. There’s no known astrophysical event that can tidily explain this line—but the collision of dark matter particles might. If that were the case, it would be a major discovery: Once physicists spot the products of such an annihilation, they could begin to understand the particles that collided.

But there was a catch: Weniger is not a member of the Fermi-LAT collaboration and therefore cannot be able to account for the quirks of their instrument. What was needed was a weigh-in from Fermi-LAT collaboration physicists; they know the data best and would be able to confirm any hint of dark matter.

That confirmation—though very qualified—came earlier this month at the Fourth International Fermi Symposium. “We do see a line at the galactic center but at lower significance than others have seen,” The Ohio State University physicist and collaborator Andrea Albert says.

Specifically, when Albert and colleagues looked within a certain region of the galactic center, they saw a prominent gamma-ray line with an energy of 135 giga–electron volts (GeV) with 3.35 sigma local significance.* This is close enough to Weniger’s observations to infer that this is the line he spotted as well. There’s even a second, much less pronounced line that could support the conclusion that this is dark matter. If dark matter really is what’s producing the gamma-ray line in the galactic center, physicists would predict that it could produce additional signals nearby, annihilating and releasing other particles as well as gamma-rays. The Fermi-LAT collaboration has some evidence of a second line that meshes well with this theoretical prediction.

But there is a problem with the 135 GeV gamma-ray line. When Fermi–LAT physicists looked at data from the Earth limb, or outer rim of the atmosphere, they found another linelike bump in the data at 135 GeV. Put simply, that region should be bump-free. The presence of a line at the same energy level in two different data sets suggests that these could be aberrations introduced by data processing.

Then again, the Earth-limb finding could just be a coincidence—albeit an eerie one.“For now, we cannot exclude the possibility that the line in the galactic center is a dark matter line,” Albert says. “Within a year we hope to have an answer.”

*Clarification (11/19/2012): This sentence was edited after posting. The line’s 3.35 sigma only reflects local significance; its global significance was less than 2 sigma.

About the Author: Daisy Yuhas is an associate editor at Scientific American Mind. You can follow her on Twitter, @daisyyuhas

22 Comments

Theoretical physicists seem so desperate to find the putative WIMPs (AWOL for over 40 years) that they will latch onto almost any phenomenon and crown it a possible discovery of WIMPs. The number of false-positives over the last 40 years is amazing, and still the beat goes on.

Time for new ideas? Time for studying nature instead of trying to squeeze nature into an ill-fitting theoretical box?

Particle physicists speculate that WIMPs would congregate at the galactic center because of their gravitational interaction – but in that case wouldn’t they all eventually fall into the galactic supermassive black hole?

Of course, if dark matter primarily existed at the galaxy periphery (see the artist’s rendering in the inset above), as required to produce the ‘flat’ rotation curves of the visible galaxy in accordance with Keplerian projections, experimental particle physicists would be wasting their time trying to detect WIMPs here on Earth…

If you wanted to find and communicate with other lifeforms in the galaxy, where’s the one single natural place to meet up?

That’s right, within a few parsecs of Sgr A*.

This is not a crackpot idea; Sgr A* is the center of the galaxy, and we’ve observed it, just like a star on the other side of the galaxy could. It makes sense that some ET intelligence with advanced technology would turn this into a galactic rally point.

This may end up being the most likely explanation. It’s also testable; if we can find an inherent structure in those gamma ray lines (reducing amplitudes: harmonics perhaps?), then obviously they’re some form of communication or beacon. If it’s without any kind of structure, THEN we should start speculating about dark matter.

I agree with Josh, if there were another form of intelligence in the galaxy, this would be an ideal spot for a beacon for first contact. Not saying that is what it is, but it’s an intriguing idea and warrants signals intelligence analysis.

It’s as though no one commenting any idea about how science works. Science gets to the truth by, as Feynman said, first “guessing”. There is nothing unusual going on here except pseudo-scientists thinking they have the answer, and their answer being that science are always wrong. It’s tiresome.

What is there to comment about here? A hypothesis was invoked according to present understandings to explain some recently observed phenomena. Research will performed to understand and attempt explain and determine if the hypothesis is supported or not.

That is all there is to say. Any other comments are just blowing smoke.

LarryW – You certainly seem to consider yourself the final authority in this dark matter, although you only complained about other commentators in the most general terms. As far as I can tell you’re not capable of evaluating any specific issues raised – do you know anything about dark matter? You fail to recognize that the “observed” gamma ray ‘phenomena’ was identified only by a small team of independent researchers, and that the FERMI telescope researchers are aware of some specific shortcomings in their equipment’s ability to properly observe those gamma rays and are planning corrective action.

Moreover, this report was not the result of observational findings, but of a concerted search of observational data to identify potential dark matter annihilations. Is searching for evidence to support a preexisting hypothesis following proper scientific method?

Is that all you’ve got to say? Perhaps what seems like smoke to you is actually a reflection of your ignorance about this subject.

Yes, there are ‘dark doing’ at the center of the Milky Way.
Nature’s absolute logic, equator of self-contradiction,oneness of pairness, reigns at galactic centers.
It seems to me that Femi-LAT has it right.

just more questions , now that the gamma range has been identified could the environment of other black holes be seen as sources , could this phenom have been going on but too infrquently ? if this is a result of dark matter being concentrated around gravity points could indicate a reason for the increased speed of universal exspansion ? does the altered gamma patern predict a multi particle state of dark matter ?

justyntoo – Please take a look at the disperse configuration of dark matter shown in the inset artist’s rendering, generally consistent with the requirements to produce flat galaxy rotation curves for observed matter. To fit observed rotation to Keplerian rotation curves, up to 90% of total galaxy mass must be located beyond the radius of the visible galaxy.

Dear Sir,
Is there no other sensible explanation to explain the galaxy rotation curve? Why not use the Keplerian model differently?

If we assume the universe as a bigger replica of the solar system where galactic clusters represent planets, we may get a different idea. The speeding galaxy phenomenon is observed only at large distance scales and not at local galactic scales. In that case, there is no need to suggest an expanding universe, because if the universe is expanding, then even the solar system should also be expanding. The planets may be solid blocks, the inter-planetary space should show this expansion.

Coming back to the galaxy rotation club, we need not think the rotation as the rotation of a wheel. Just like the solar system is one, but different planets move at different velocities sometimes appearing to separate away and at other times closing in, it is possible that the universe is showing similar features. Our observation of the speeding galactic clusters is insignificant in cosmic scales. May be in future we will observe the reverse phenomenon.

Durgadas Datta published a paper named–Balloon inside balloon theory of matter and antimatter universe on opposite entropy path producing dark energy or gravitoethertons at common boundary by annihilation and injected into our universe to cause gravity,laws , accelerating expansion etc etc. As per his theory the gravitoethertons are mono magnetic couplings getting focussed at center of gravity of all objects and as such our earths core is molten iron as well as center of our galaxy is a soup of dark energy most concentrated we loosely call black hole. The universe and earth etc are magnetic due to mono magnetism of gravitoethertons. Now his theory is showing those predictions long back declared in various science forums. Our universe is gravitoethertons soup of various concentration as a result non isotropic and speed of light also vary as it travel through this soup. Our all estimates based on Einstein is to be reviewed as laws also may be varying across our universe. Our universe is more dynamic and non uniform because of dark energy soup and our theories of quantum mechanics never considered the interaction of dark energy at atomic level. Read his paper–MISJUDGEMENT BY NEWTON published in ASTRONOMY.NET in year 2002 — long back to re establish ether or dark energy and declared both Newton and Einstein may be approx . right for our solar system but outer solar system it will be wrong. No body wanted to listen to him and wasted money in gravity probe-B. Durgadas Datta also said atomic structure is not what is known today , but it is balloon inside balloon films of negative and positive charges with neutron at common center. The radius of these balloons depend on number of electrons or protons. He even said that neutrons are concentrated dark energy blobs at center with magnetic force with dark energy soup inside and outside. As such there is no strong or weak force . More in his new atomic theory.

Dark matter is simply “rest” matter at a higher relativistic mass level relative to absolute space. Einstein came up with the idea of relativistic mass and then decided to use only “rest” mass and change time rather then inertial mass of a body. That worked OK until we started the GPS system and found out the rest mass in the GPS satellites are different then rest mass on earth and concluded it must be the time that is different up there BUT it is only the clocks that vobrate at different speeds NOt the time is different. einstein should have stuck with his relativistic mass instead of fooling around with time.http://novan.com/absolute-space.htm

Dark matter has been termed as “dark” since matter of this type does not interact with other normal matter or normal radiations electromagnetically. Presence of dark matter has been predicted thru gravitational influence only. This implies dark matter unlike baryonik matter neither absorbs nor radiates e.m radiations. E.m radiations including gamma rays are emitted when normal baryonik matter and anti-matter annihilate each other. For example, gamma rays emanate out when electron and positron collide and annihilate.

Normal baryonik matter and e.m radiations act in tandem in coupled pair at both absorption and emission stages.

In view of above, why annihilation of dark matter should not emit gamma rays — which are normal e.m radiation emitting from normal barynok matter.

Even if some radiations should emerge out from dark matter, such radiations should of some “dark radiations” whose nature should be quite different than normal e.m radiations. We know nothing about such” dark radiations”. If there is difference in the properties of barynoik matter and dark matter why there should be no difference in the properties in radiations emitted from each of the matter?

Had annihilation of dark matter emitted out gamma rays ( normal e.m radiations), dark matter would have interacted electromagnetically and dark matter could also have been detected thru e.m radiations like normal barynik matter. This being not the case, annihilation of dark matter should not emit e.m radiations ( gamma rays)

Therefore, whole basis of emission of gamma rays from the center of MW or from any other region for establishing the presence of dark matter appears a faulty one.

“In that case, there is no need to suggest an expanding universe, because if the universe is expanding, then even the solar system should also be expanding.”

Leave aside solar system which is of very very miniscule distance in terms of cosmological scales. Cosmological red shift, which has been interpreted to arise from expansion of universe, has not been detected even for distance running into million of light years. Our MW galaxy being about 1,00,000 light years apart also has not shown any cosmological red shift. Compared to this, our solar system is only a fraction of a light year wide.

Astronomers have observed cosmological red shift from distances greater than 300 mparsec ( approx 1 billion light years, 1 parsec = 3.26 light years). Within this very large distance of 1 billion light years, a large nos. of galaxies are located which have not demonstrated any cosmological red shift. Why? There is no convincing explanation from scientific quarters ( at least I don’t know)